The present invention generally relates to electrodes and, more particularly, to medical electrodes for transcutaneous stimulation of nerves and/or muscles or monitoring of biological or physiological electrical potentials in a body.
Transcutaneous electrical nerve stimulation electrodes are useful in pain control while electrical muscle stimulation electrodes are useful in maintaining and developing tissue. Stimulating electrodes of this type may also incorporate a medicament for iontophoreses, that is, the introduction of a topically applied physiologically active ion into the epidermis and mucus membranes of the body by the use of electrical current.
Monitoring electrodes are, used, for example, in conjunction with monitoring devices to produce, for example, electroencephalograms (EEG), electromyograms (EMG) and electrocardiographs (ECG).
Because of the curved nature of the epidermis layer on to which the electrodes are applied, the flexibility of the electrode is of paramount importance.
In additions, physical and electrical stability of the electrodes must be maintained over long periods of application. In that regard, a specific difficulty in heretofore developed electrodes manifest itself in the electrical connection of the electrode to an outside power source or monitoring device.
That is, some type of lead wire must be connected to the electrode and maintain constant electrically continuity between the lead wire and the electrode. In the case of stimulation electrodes, electrical continuity is required to provide constant uniform current distribution. Disruption of current, i.e., an abrupt connect/disconnect occurrence, can cause a startling effect on a body. In the case of monitoring electrodes, electrical continuity is required for uniform sensing of electrical potential. Interruption of electrical continuity in monitoring electrodes may result in xe2x80x9cfalse alarmsxe2x80x9d, such as spurious electrical output, or open circuit conditions in which information flow is disrupted.
Typically the lead wire is soldered, welded, cemented or otherwise held in direct contact with a highly conductive element of an electrode such as a metallic foil, mesh or conductive woven fabrics or the like. These conductive elements are coupled to a body though a conductive gel and covered with a non-conductive backing to prevent undesired contact from a reverse side of the electrode with the conductive element.
This necessity of direct contact between a lead wire and the conductive element has limited the performance of medical electrodes to this date.
The present invention provides for an electrode having a conductive element which makes no direct contact to an electrical lead wire or connector thus eliminating problems associated with heretofore required interconnection.
A medical electrode in accordance with the present invention, generally includes a first conductive polymerizable gel layer for electrically coupling the electrode to a body along with a flexible electrical conductor disposed on the first gel layer. The electrical conductor may be a conductive fabric or sheet comprised of conductive and non-conductive elements. Other combinations are also contemplated as part of the present invention, as, for example, a sheet with low conductivity with a highly conductive layer disposed thereon.
A second conductive polymerizable gel layer is provided and disposed on the flexible electrical conductor to suspend or float the conductor between the first and second gels.
In one embodiment, the conductor is porous and importantly, the first and second gel layers are polymerized with one another through the porous conductor.
This polymerization through the flexible porous electrical conductor is preferred in order to not only secure the flexible porous electrical conductor within a unitary gel consisting of the first and second layers, but also to provide intimate electrical contact between the flexible porous electrical conductor and the gel.
It should be appreciated that the flexible porous electrical conductor is not contacted by any other medium but the gel and hence the conductor can be considered as xe2x80x9cfloatingxe2x80x9d within the gel.
In addition, the flexible porous electrical conductor provides structural integrity to the gel. Because it is laminated or bonded therein through the polymerization of the gels and embedded therein, the flexible porous electrical conductor provides structural integrity to the gel.
An electrical connector is provided and disposed in contact with the second gel layer and insulative backing is adhered to the second gel layer. In this manner, initial electrical connection to the flexible porous electrical conductor is made through the gel.
In one embodiment of the present invention, the electrical connector extends through the backing for electrical access thereto. This structure enables secure fastening of the electrical connector, which may be a snap connector, because it is physically surrounded by the backing.
In order to enhance the electrical coupling between the electrical conductor and the connector, the second gel layer may be. more electrically conductive than the first gel layer. In this manner the second gel layer provides for enhanced electrical distribution across the conductor and the first layer thereafter couples this evenly distributed current profile to the body.
More particularly, the flexible porous conductor may comprise a non-electrically conductive sheet with an electrical grid disposed thereon. Preferably the electrical grid comprises an electrically conductive ink pattern printed on the non-electrically conductive sheet.
In one embodiment of the present invention, suitable for stimulation electrodes, the ink pattern includes a perimeter with interconnecting ink lines with the perimeter being set apart from edges of the non-electrically conducted sheet. This configuration provides a roll off of electrical current from the edges of the electrode.
In another embodiment, suitable for monitoring electrodes, the conductor may have dimensions substantially equal to the first and second gel dimensions. In this instance greater electrode monitoring sensitivity is afforded the electrode.
In yet another embodiment of the present invention, the electrical contact may include a lead wire in contact with a second gel layer and a second conductive grid may be utilized to enhance the electrical coupling therebetween.
Further embodiments of medical electrodes in accordance with the present invention include a first conductive polymerizable, gel layer for electrically coupling the electrode to a body and a medicament containing conductive polymerizable gel layer polymerized or bonded to the first gel layer.
A flexible porous electrical conductor is disposed on the medicament containing gel and a second conductive polymerizable gel layer is disposed on a flexible porous electrical conductor and polymerized with the medicament containing gel through the porous conductor. An electrical connector is disposed in contact with the second gel layer and an insulative backing is adhered to the second gel layer.